by Randy Muller
A year ago, our first trip to this site had yielded the darkest skies I had ever experienced, as fog in the Central Valley suppressed the light pollution from the Sacramento-Stockton megalopolis.
Although I knew fog was certainly a desirable possibility, I was just hoping for clear skies. As I made the very pleasant drive to the site, I noticed a promising break in the clouds to the north. During the drive up, I realized I had forgotten the light shield covering the screen of my laptop. I briefly considered turning around and getting it, but since I normally continue to bring my paper and book charts, I decided I could still observe without my laptop charts, so I pressed on.
When I arrived at the site, the clouds covered the sky, but I set up anyway because I knew it was going to be variable. I just didn't know how variable. My plan for the evening was to view faint galaxies I had not seen before whereever they could be found. I presumed I would be observing in Eridanus or Cetus. With the clouds, it became obvious that I could not carry out this plan effectively, so I fell to my backup plan of observing whatever was visible, whether I had seen it before or not. This gave me considerable flexibility.
Eventually it became dark. The cloud cover was changing constantly but everpresent. But shining through the clouds were Jupiter and Saturn, so we turned our scopes on these gas giants beyond the asteroid belt.
The North Equatorial Belt, in contrast, was thicker and visibly more turbulent. There were wisps and bumps making the boundary decidedly non-linear. I didn't observe any motion, but the appearance of the belt seemed like a snapshot of a riot of activity. Three large festoons were erupting from the southern boundary of the belt, and billowing into the Equatorial Zone.
The Equatorial Belt, at the center of the EZ, though thin and weak and broken in spots, was definitely present. It was fun to conjecture that the festoons were feeding dark brownish pigment into the EB, although I have no idea whether this is really true or not.
The terminator was visible on the east (celestial) side of the planet as a qualitative difference in appearance of the east and west limbs of the planet. The limb on the west side was very sharp and distinct, while the east side had a softer edge that seemed to blend into darkness, albeit in a small area.
I was able to identify the four Galillean moons by their order, brightness and color differences. Gary confirmed my guesses with his laptop running Linux and XEphem. It's actually not that hard to do, given a little eyepiece time and being sure to identify them later whenever observing them. After a little study, each one has its own character. Ganymede is the brightest, Io has a very slight yellowish tint, and Callisto is dimmest.
Later I observed the Great Red Spot Hollow rotate into view, from west to east. By this time, the seeing had deteriorated, and not as much detail was visible in the cloudtops. I checked the hollow a hint of color, but absolutely none was visible. The last time I had looked at the Great Red Spot on December 4, 1999, it had a similar colorless appearance. The last time I saw distinct reddish color in this feature was October 2, 1999.
Another satellite was easily visible on the southeastern side. This one turned out to be Rhea. I eagerly asked Gary what other ones there were. After studying at the chart, we located Tethys just west of the rings, Dione just north of the planet and Enceladus just east of the rings. Enceladus was by far the most difficult to see, and we only saw it because we knew exactly where to look. It was only visible with averted vision by looking directly at Rhea.
The shadow of Saturn on the rear side of the rings was very prominent, and gave the whole system a startling 3D look. The Cassini Division was obvious. Having both of these planets so high in the sky with the generally better seeing is a real visual treat.
It had been dewing moderately, but the trend suddenly reversed itself, and it seemed to be drying out. The air began smelling dry. Also at this time, the entire sky clouded up, so Gary and I jabbered for a while about what we had seen up to this point. At the beginning of the evening, it seemed like the whole evening would be wasted, but we had already salvaged quite a bit of observing to make the whole thing worthwile.
After this, random parts of the sky began clearing, so I decided to take a look the Great Nebula in Orion. It was partially covered with clouds and strangely muted, but 5 stars were visible in the Trapezium. The 6th was hidden by the bloated "C" star, as shown on the diagram on page 1327 of the revised edition of Burnham's Celestial Handbook. Orion was still not very high in the sky at this point, and later I was barely able to see "F" intermittently.
Perseus seemed clear, so I oggled the Double Cluster, both naked eye and with my scope for a little while. I then went back to Auriga as I had opportunity, and took a good look at M38, with its attendant, but smaller and dimmer NGC 1907. These open clusters contrasted sharply in size and brightness, and are interesting because they are so close.
Rather suddenly, the entire sky cleared. There was no more haze around Jupiter and Saturn. I quickly decided to resume my original plan: Chasing faint galaxies I hadn't seen before, in this case in Eridanus.
I began with NGC 1417, a magnitude 12.1 galaxy which I hopped to from 17 Eridani, which star was easily visible to the naked eye. From 17 Eridani, I hopped east 2 degrees across a little triangle asterism, and then went about half a degree northeast. It was a small, but bright diffuse oval, very close to a dim star.
Next, I went back to the triangle to pick up 1376 and 1358, which I had skipped past. Although these were all listed at the same magnitude (12.1), these two seemed considerably dimmer than 1417.
Finally, I headed about a degree out past 1417 again to try for 1453, which I found easily, because it seemed fairly bright, being small, round with a concentrated center.
I was hunting for 1441 nearby, which was undoubtedly too faint for the conditions, when clouds covered the sky again. It was 10pm, and my frustration with the poor conditions peaked, so I decided to pack up. Of course the whole sky appeared clear for the whole time I was driving home, except for when I entered the dreaded Sacramento Valley tule fog as I neared the valley floor.
In spite of its shortness, it was a great night for observing planetary cloud tops through earthly cloud bottoms and I even got a few new galaxies in Eridanus.
| Date | January 8, 2000 5:30pm-10:00pm (0130-0600 Jan 9 UT) |
|---|---|
| Location | Fiddletown, CA (38.5N 120.75W) |
| Altitude | ~2600 ft. |
| Instrument | Orion DSE 10" f/5.6 dob-newt |
| Oculars | 7.5, 10, 17, 26mm Sirius Plossls |
| Seeing | 8/10 |
| Transparency | 6/10 |